Knife sharpener



FIG. 1 is a perspective view of a knife sharpener showing my new design;

FIG. 2 is another perspective view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a back elevation view thereof;

FIG. 5 is an enlarged left side view thereof;

FIG. 6 is an enlarged right side view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof.

CLAIM The ornamental design for a knife sharpener, as shown anddescribed.